Line simulators are widely used in communication laboratories and communication device development to test functionality and performance of communication systems and devices. For example, to test a communication device the communication device is coupled to a line simulator, which simulates the behavior of a communication line (for example wireline) to which the communication device is intended to be coupled during actual deployment later. In other words, the line simulator simulates characteristics of an actual physical communication line. For digital subscriber line (DSL) systems the simulated line may be a subscriber loop, for example a twisted wire pair. Digital subscriber line or DSL as used herein generically refers to any of a plurality of DSL flavours, like ADSL, ADSL2, VDSL, VDSL2 and is intended to include also the upcoming G.fast.
Most conventional line simulators are single line devices, which simulate only a single communication line. It is difficult to use such line simulators to also investigate effects of crosstalk between a plurality of lines on the line data transmission. To emulate crosstalk at least to some extent, such conventional line simulators may create a specific noise on the line.
For crosstalk cancellation systems like vectoring systems employed in some DSL flavours (for example as defined in ITU-T G.993.5 or as used in G.fast), crosstalk such as far-end crosstalk (FEXT) cannot sufficiently be emulated by simply inserting noise. Therefore, in such cases a multi-line simulator with coupling devices between different lines is required to simulate crosstalk. Such devices, however, only exist for comparatively low frequencies as used for example in VDSL, for example up to about 30 MHz.
However, for example other communication standards like the upcoming G.fast also use higher frequencies, for example up to about 212 MHz. Conventional multi-line simulators may not be able to simulate the characteristics of the communication lines with sufficient accuracy, in particular for high frequencies.